Optical communication systems require the laying down of numerous optical cables and fibres. These are connected together using various forms of optical fibre hardware such as optical joints, e.g. optical fibre closures or splicing enclosures. Optical joints are used for storing and managing optical cable and fibre connections and providing work areas in which optical cables and fibres can be worked, for example coupled, split, spliced, terminated or the like. Hereinafter, the operations which are carried out on the optical cables and/or optical fibres—such as coupling, splitting, splicing, terminating—are referred, to as working the cables/fibres. In the optical joint, the cables/fibres can be worked, stored and then sealed from the environment.
Typically, optical joints receive a plurality of optical cables, each in turn having at least one optical fibre. This generally causes congestion of the optical joints due to intertwining of the optical cables and/or of the optical fibres during storage and installation. As more optical cables and fibres are connected to an optical communication system, optical cable and fibre storage, e.g. within the optical joints, becomes evermore difficult.
Traditionally, several optical cables enter an optical joint and are managed in fibre management systems that distribute the fibre throughout the joint. The cables may be secured within the optical joint and later worked, e.g. joined together by butt splicing according to which at least some of the optical fibres are broken out from each cable and spliced together within splicing trays. The remaining unused fibres are simply stored within splicing trays or storage bays of the optical joint until required. However, although this may organise the cable/fibres, it also adds to the total congestion within the optical joint and can be considered as being wasteful of the available optical cable/fibre resources in terms of space and used/unused fibre. As more cables are installed, there is an increased likelihood of optical cable and fibre damage as bending the optical cable and fibres around each other risks bending them beyond their minimum bend radius.
Typically all the optical fibres are broken out of each optical cable upon entering the joint, and the fibre management system deals with all optical fibre by storing or working it. The broken out fibres may be protected with flexible transport tubes, however, the tubes are still required to be stored for excessively lengthy runs of fibre. Alternatively, only those fibres that are required to be worked are broken out of the optical cable, while the remaining optical cable is then stored within the optical joint for future use. However, the remaining optical fibre and cable remain unused and simply take up valuable space within the optical joint.
There are numerous fibre management systems for storing and distributing fibres within a splicing tray. For instance document U.S. Pat. No. 6,427,045 discloses a splice tray for use in splicing fibre optic cables, said splice tray having an outer periphery and a cable splicing area inwardly of the outer periphery. A main cable guideway for receiving a pair of side-by-side cables to be spliced extends along a portion of the outer periphery adjacent thereto. The main cable guideway splits into first and second continuation guideways, the first of which curves inwardly from the outer periphery to intersection with the splicing area from one direction. The second continuation guideway continues along another portion of the outer periphery to intersection with the splicing area from another direction. The two fibre optic cables that extend along the main guideway are separated to extend through the first and second continuation guideways to the splicing area for being joined together in a splice. A cable looping device is provided in the splicing area for receiving cable loops to take up slack, and a splice receiving recess is provided in the splice area for holding a splice. A housing for the splice tray includes a vertical case having a door hinged to the bottom portion thereof for swinging movement about a horizontal hinge axis between a vertical closed position and a horizontal open position. The splice tray is attached to the inside of the door for receiving a pair of cables that extend from the case and across the hinge to the splice tray. An integral inclined guideway extension on the splice tray extends toward the hinge axis along an inclined door bottom wall for receiving the cables.
According to U.S. Pat. No. 6,427,045 the guideways act as channels for routing to the splicing area only two optical cables, with only one optical fibre in each. In fact, since the cables are stored within a central cable looping device, the cables cannot contain more than one optical fibre as any more fibres would not allow the cables to be bent around the central spool. Moreover, since the cables are stored within a cable looping device which is placed centrally with respect to the splice tray, the cable storage is not efficiently performed principally for the reason that a large area of the splice tray is unused. Furthermore, the splice tray according to U.S. Pat. No. 6,427,045 does not provide for a storage area for the optical fibres to be worked, e.g. to be spliced.
Alternative solutions attempt to alleviate optical cable and fibre congestion and damage by storing and guiding optical cables and fibres from separate storage bays to optical fibre trays for use in optical joints. For instance, documents U.S. Pat. No. 6,501,898, U.S. Pat. No. 6,539,160 and U.S. Pat. No. 5,278,933 disclose fibre management systems for guiding and storing optical cables/ribbon cables and optical fibres, respectively.
Document U.S. Pat. No. 6,501,898 relates to an arrangement for handling optical fibres in a confined or limited space, such as connecting, reorganizing and/or cross-coupling optical fibres in a cassette without said fibres intersecting one another. By providing a cassette with looping channels, the optical fibre cables can be organized in a controlled fashion without needing to cross. This arrangement is provided with means for guiding and coiling the optical fibre cables prior to stripping respective cables and mutually separating the enclosed optical fibres in an optical fibre cassette.
According to this document cable coiling and guiding devices are located in the central portion of the bottom part of the connecting box arrangement which comprises a plurality of cassettes (splicing trays) that are stacked for receiving and storing broken-out optical fibres. This results in an inefficient and unsatisfactory use of available space within the optical joint.
Document U.S. Pat. No. 6,539,160 relates to a fibre optic closure, which includes a panel assembly having at least two panels hinged to one another. The panel assembly includes a storage bay sandwiched between a pair of fibre management and connection assemblies. Each fibre management and connection assembly includes a sleeve connector panel that supports at least one sleeve connector array for establishing optical fibre connections. The splice panel having splice tube holders is also provided for establishing splices. The storage bay is disposed between upper and lower splice panels. Moreover, retaining and routing clips are used for keeping in place and guiding the fibres and/or the optical fibre cables in the splice tray.
According to this document the splice panel (tray) does not allow for storing both the optical cable and the optical fibres, the storage thereof being demanded to a storage bay interposed between two splice panels of the fibre optic closure.
Document U.S. Pat. No. 5,278,933 discloses a fibre optic splice organizer for storing optical fibre splices and the slack associated therewith to permit ready separation of the optical fibres. The splice organizer includes a generally rectangular base, splice securing slots on the base, and optical fibre guides for guiding slack portions of first and second optical fibre groups from a first end of the base, along respective portions of the base adjacent the first and second sides thereof, into a plurality of overlying slack loops adjacent the second end of the base, and back to the splice securing means from respective first and second sides of the base. The slack optical fibres, including the overlying respective slack loop, of the first and second optical fibre groups, form a figure-eight pattern on the base and are thus readily separable from each other.
According to this document a storage solution is provided that guides and binds bundles of broken out optical fibres together, stringing them over, around and behind the splicing tray. This solution provides an inefficient use of storage and also hampers access to the splicing bays as bundles of fibres will need to be removed and untangled. This inevitably increases the risk of accidental bending of the fibres beyond their minimum bend radii.
As mentioned above, clamps and ties are used for securing optical cable or fibre within the storage bays of U.S. Pat. No. 6,539,160 or the bundles of fibres in the splicing tray of U.S. Pat. No. 5,278,933. The clamps and ties need to be loosened or cut when optical cables or bundles fibres are re-routed to splicing bays or elsewhere. The use of clamps and cable ties can cause fatigue of the optical cable material at specific points along the cable. Similarly, the fragile optical fibres at these points can be damaged. Further damage can be caused during installation and maintenance as the clamps or ties are tightened/loosened/removed or the hinged covers are removed and replaced when installing/accessing/re-routing the optical cables and bundles of fibres.
In addition, the clamps or ties do not fully support the optical cables or fibres, which are only supported at specific points around the storage bays or splicing trays. This means that spaced lengths of cable and fibre are completely unsupported, said unsupported lengths being possibly bent in towards the centre of the storage bays or splicing tray and stresses being possibly exerted on these unsupported lengths while they are installed, maintained, and held within the storage bay. Therefore, this aspect can further contribute to damage and breakage of the cables/fibres.
The problems of storage and congestion of optical cables within optical joints continue to multiply as the number of splice trays and/or optical cables progressively increases to cope with the demand for high speed communications equipment and capacity.
The Applicant has perceived the need of efficiently organizing the space within a joint closure, and in particular within a splice tray, in order to minimise the size and congestion of the optical joints, meanwhile without causing any damage or breakage to the optical cables and/or fibres when the joint is opened/closed or the trays are moved during installation and maintenance thereof.